cannot deselect radio button with jquery

I'm having a problem with getting a radio button to deselect. I've got the following buttons: <input type="radio" name="sex" value="Male">Male</input> <input type="radio" name="sex" value="Female">Female</input> <input type="radio" name="sex" value="Unknown">Unknown</input> In the pagebeforeshow I've got: $('input:radio[name=sex]').attr('checked',false); The first time the page displays, no button is selected. I select a button and dismiss then page and when I redisplay the page the radio button is still selected, What am I missing?